5-cinnamoyl-pyrrole-2-acetic acids and esters

ABSTRACT

Compounds of the class of 5-acyl-pyrrole-2-acetic acids useful for their analgetic activity and the corresponding lower-alkyl esters used as precursors thereof.

United States Patent [19] Carson Aug. 28, 1973 5-CINNAMOYL-PYRROLE-2-ACETIC ACIDS AND ESTERS [7 5] Inventor: John Robert Carson, Norristown, Pa.

[73] Assignee: McNeil] Laboratories, Inc., Fort Washington, Pa.

[22] Filed: Jan. 21, 1972 [21} Appl. No.: 219,862

OTHER PUBLICATIONS Turbanti et al., Chimica Therapeutica, Vol. II, pages Randall et al., published application 62,242 (Jan. 22, l952)published in 654 CG 1152 through pages 1 154 in abstract form.

Primary Examiner-John D. Randolph Attorney-Salvatore R. Conte et al.

[57] ABSTRACT Compounds of the class of 5-acyl-pyrrole-2-acetic acids useful for their analgetic activity and the corresponding lower-alkyl esters used as precursors thereof.

5 Claims, No Drawings 5-CINNAMOYL-PYRROLE-2-ACETIC ACIDS AND ESTERS BACKGROUND OF THE INVENTION The invention pertains to the field of 5-cinnamoyl-pyrrole-Z-acetic acids which demonstrate analgetic activity. The subject-acids differ in structure from the prior art (see Belgian Patent No. 762,060) by having a cinnamoyl function in the 5-position rather than a benzoyl function.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The novel 5-cinnamoyl-pyrrole-2-acetic acids of this invention may be structurally represented by the formula:

wherein Ar is a member selected from the group consisting of phenyl, halophenyl, loweralkylphenyl and loweralkoxyphenyl; and R is a member selected from the group consisting of hydrogen and loweralkyl, preferably methyl.

As used herein, loweralkyl and loweralkoxy" may be straight or branch chained and have from 1 to about 5 carbon atoms, such as, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl and the like alkyls, and respectively, methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentoxy and the like alkoxys. The term halo is generic to chloro, bromo, fluoro and iodo, preferably chloro.

The compounds of formula (I) may be prepared by a Friedel-Crafts reaction between an appropriate cinnamoyl halide (II), preferably the chloride, and an appropriate loweralkyl N-R-pyrrole-Z-acetate (III) in the presence of a Lewis acid, preferably a metallic halide such as aluminum chloride, stannic chloride and the like, in a suitable solvent such as is typically employed in a Friedel-Crafts reaction, for example, methylene chloride, 1,2-dichloroethane, carbon disulfide, nitrobenzene and the like, followed by conversion of the thus-obtained 5-cynnamoyl-pyrrole-2-acetic acid ester (IV) to the corresponding free carboxylic acid form (I) by conventional esterto-acid hydrolysis, for example, by refluxing the ester with aqueous alkali. The foregoing reactions may be illustrated by the following schematic diagram:

(II) (III) (I) The cinnamoyl chlorides (II) are generally known and may be obtained by transformation of the corre- Time Interval (mins.) After oral administration 0 I5 30 45 m. at mgJkg 3/10 3H0 2/10 2/10 Control 9/l0 9/10 6/l0 3/l0 The esters of formula (IV) are also deemed to be novel and, in view of their utility as precursors for pre paring the acids of formula (I), they constitute an additional feature of this invention.

The following examples are intended to illustrate, but not to limit, the scope of the present invention.

EXAMPLE I Ethyl S-cinnamoyll -methylpyrrole-2-acetate A suspension of 22 g. (0.020 mole) aluminum chloride in ml. methylene chloride is cooled externally with an ice bath. To this is added 33.2 g. (0.02 mole) of melted cinnamoyl chloride all at once. The resultant solution is added dropwise (over 15 minutes) to a solution of 33.2 g. (0.020 mole) ethyl l-methylpyrrole- 2-acetate in 120 ml. methylene chloride while cooling externally with an ice bath. After the addition, the ice bath is removed and the solution stirred for 45 minutes, and then poured into ice acidified with dilute hydrochloric acid. The organic phase is separated and washed consecutively with 3N hydrochloric acid, N,N- dimethyl-l,3-propanediamine, 3N hydrochloric acid and saturated sodium chloride solution, and then dried with anhydrous magnesium sulfate. The solvent is evaporated. The residue is dissolved in;benzene and chromatographed on a column packed with two pounds of acid washed alumina. It is eluted with benzene and the front running material is collected. The solvent is evaporated. The product, ethyl S-cinnamoyl-l-methylpyrrole-2-acetate, is isolated from the residue upon trituration with methanol and purified by recrystallization in methanol; m.p. 5l53C.

EXAMPLE II By repeating the acylation procedure of Example I, except that an equivalent quantity-each of p-chloro-, a-chloro-, p-bromo-, p-methyl-, -p-methoxyand pethoxy-cinnamoyl chloride, dissolved in methylene chloride, is used as the acylating'agent in place of the cinnamoyl chloride used therein, there are obtained, as respective products, the following:

ethyl 5-( p-chloro-cinnamoyl)- l methylpyrrole- Z-acetate;

ethyl a-chloro-cinnam oyl 1 -methylpyrrole- Z-acetate;

ethyl 5-( p-brom'o-cinnamoyl l -methylpyrrole- 2-acetate;

ethyl 5-( p-methyl-cinnamoyl l -methylpyrrole- Z-acetate;

ethyl 5 -(p-methoxy-cinnamoyl)-1-methylpyrrole- Z-acetate; and ethyl 5-( p-ethoxy-cinnamoyl l -methylpyrrole- Z-acetate.

EXAMPLE Ill The procedure of Example I is followed, except that an equivalent quantity of ethyl pyrrole-Z-acetate is used in place of the ethyl l-methyl-pyrrole-Z-acetate used therein, and an equivalent amount of an appropriate cinnamoyl chloride acylating agent is used, to yield, as the final respective products:

ethyl 5-cinnamoyl-pyrrole-Z-acetate;

ethyl 5-(p-chloro-cinnamoyl)-pyrrole-2-acetate;

ethyl S-(p-methyl-cinnamoyl)-pyrrole-2-acetate; and

ethyl 5-(p-ethoxy-cinnarnoyl)-pyrrole-2-acetate.

EXAMPLE IV CH2COOH S-Cinnarnoyll -methylpyrrole-2-acetic acid A solution of 2.34 g. (7.9 X mole) ethyl 5- cinnamoyl-l-methylpyrrole-2-acetate in 10 ml. methanol is brought to reflux. To the refluxing solution is added 8.3 ml. of 1N sodium hydroxide dropwise. After the addition, the solution is heated at reflux for minutes. The methanol is then evaporated. The resultant suspension is poured into dilute hydrochloric acid. A precipitate of S-cinnamoyl-l-methylpyrrole-2-acetic acid forms which is collected by filtration and purified by recrystallization in methanol; m.p. l70-2C.

EXAMPLE V The hydrolysis procedure of Exarnpe IV is repeated, except that an equivalent quantity of each of the esters obtained in Examples ll and Ill are used in place of the ethyl S-cinnamoyl-l-methylpyrrole-2-acetate used in wherein Ar is a member selected from the group consisting of phenyl, halophenyl, loweralkylphenyl and loweralkoxyphenyl; and R is a member selected from the group consisting of hydrogen and loweralkyl.

2. S-CinnamoyH-methylpyrrole-2-acetic acid.

3. A loweralkyl 5cinnamoyl-pyrrole-Z-acetate of the formula:

l l l m-o H=C 11-0 0i )4? 11 -0 0 o (loweralkyl) wherein Ar is a member selected from the group consisting of phenyl, halophenyl, loweralkylphenyl and loweralkoxyphenyl; and R is a member selected from the group consisting of hydrogen and loweralkyl.

4. Loweralkyl 5 -cinnamoyll -methylpyrrole- 2-acetate.

5. Ethyl S-cinnarnoyll -methylpyrrole-2-acetate. 

2. 5-Cinnamoyl-1-methylpyrrole-2-acetic acid.
 3. A loweralkyl 5-cinnamoyl-pyrrole-2-acetate of the formula:
 4. Loweralkyl 5-cinnamoyl-1-methylpyrrole-2-acetate.
 5. Ethyl 5-cinnamoyl-1-methylpyrrole-2-acetate. 